boldness in fishes: a selection tool for aquaculture or a...

Boldness in fishes: A selection tool for aquaculture or a personality type with no apparent return?

Associate ProfessorPeter Vilhelm SkovTechnical University of DenmarkSection for Aquaculture

DTU Aqua, Technical University of Denmark

Danish aquaculture production

8 February 2018Aquaculture in DK / University of Stirling2


SpeciesAtlantic salmon (Salmo salar) Danish Salmon (1200 t/yr)Atlantic sapphire (2000 t/yr)

Kingfish (Seriola lalandi)Sashimi Royal (1200 t/yr)

Pike perch (Sander lucioperca)AquaPri (1500 t/yr)

Eel (Anguilla anguilla)~500 t/yr


DTU Aqua, Technical University of Denmark 8 February 2018Aquaculture in DK / University of Stirling4


Organic Rainbow trout (Oncorhynchus mykiss)(1100 t/yr)


GMO free

No colouring

No chemical therapeutants

Traceability

Extensive (25 kg m-3)

Good O2

Added value

Less medicine use


Promoting organic trout productionProject RobustFish

1. Is it possible to select robust fry early in the production process?2. How do non-marine lipids in the diet influence stress tolerance and disease resistance?3. Is there an market for larger production volumes of organic RBT and might conventional

farmers convert?



Stress coping style

8 February 2018Boldness in fishes / University of Stirling 7


Fry swim-up

8 February 2018Boldness in fishes / University of Stirling8


Predator present initially

Exp 1 Exp 2

N initial N end % survival N initial N end % survival

I 39 0 0.0 39 5 12.8

II 98 19 19.4 98 66 67.3

III 62 20 32.3 63 51 80.8

Hatching, emergence time, and personality..Early emergers have first access to feed and territorial space, but suffer under high predation pressure.

8 February 20189 Boldness in fishes / University of Stirling

Predator introduced after emergence

Exp 1 Exp 2

N initial N end % survival N initial N end % survival

I 39 30 76.9 25 8 32.0

II 88 45 51.1 98 12 12.2

III 51 15 29.4 62 5 8.1

Data from Brännäs (1995)


Emergence time correlates with Access to territoryFirst feeding• Dominance and boldness


DTU Aqua, Technical University of Denmark 8 February 2018Boldness in fishes / University of Stirling11


10000 fertilized all-female eggs were obtained from Seven Springs Hatchery in Ireland and incubated in a triplicate system of hatching trays. Hatching began after 365 degree days.

Swim-up began 1 week later. A total of ~9000 fry were recovered according to their time of emergence in 20% fractions.

The early, middle and late emerging fractions were retained and reared in triplicate tank systems on commercial diets.



Juvenile growth

Early Middle Late p

Initial mass (g) 14.2 ± 1.1 11.6 ± 0.5 12.1 ± 0.7 0.125 Final mass (g) 54.3 ± 2.2 48.0 ± 1.2 49.5 ± 1.6 0.092 Weight gain (g) 40.2 ± 1.1 36.5 ± 0.7 37.4 ± 1.0 0.075 FCR (g feed g-1) 0.80 ± 0.01 0.80 ± 0.00 0.80 ± 0.01 0.879 SGR (% day-1) 2.28 ± 0.11 2.50 ± 0.05 2.45 ± 0.07 0.196


Prior to any physiological or behavioural experiments, the growth of juveniles was followed from a size of 10 g to 50 g.

No indication that any fraction have better growth or feed utilization during juvenile growth.


Dropping an object into their arena and leaving it hanging (startle response and novel object): Fish seek shelter and measures are time to reappear, time to emerge, time spent exposed, approach or proximity to novel object.

Resting cortisol levels followed by low water stress challenge: Magnitude of the cortisol response and glucose mobilisation

Chase protocol: Standard metabolic rates, oxygen debt, maximum oxygen uptake rates, recovery times

Weight loss in individuals subjected to starvation for 10 days, weight gain following ad lib feeding for 7 days.

Weight loss during co-habitation with other fractions, competitive advantages in a restrictive feeding regime


Behaviour



Early Middle Late

SMR

(mg

O2

kg-1

h-1

)

020406080

100120140160180200

Early Middle Late

MM

R (m

g O

2 kg

-1 h

-1)

0

100

200

300

400

500

600

700

Metabolic rates

Early Middle Late

Met

abol

ic s

cope

(fac

toria

l)

0

1

2

3

4

5

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Metabolic rate as an indicator



Low and high SMR phenotypes


OPM database

Van Meer et al., 2008

Standard metabolic rate in rainbow trout fed diets with lipid from rapeseed oil (RO), palm kernel oil (PKO), palm oil (PO), or South Atlantic fish oil (SAFO).

Skov, unpublished


Standard metabolic rate is the sum of parts (and parts may vary)



SMR drops in response to food deprivation


SMR

(mg

O2

kg-1

h-1 )


Routine metabolismInconsistent use of terminology in oxygen use

studies. Standard, basal, resting, and routine

metabolic rate are used interchangeably by many. Standard metabolic rate, in energy

equivalents, represents <5% of energy intake.Routine metabolic rate involves a behavioural

component, as such is highly variable and may represent ≥20% of energy intake.



Oxygen debt and recovery



HPI activity and reactivity



Conclusions (I)Behavioural and physiological results demonstrate that different emergence fractions differ in certain characteristics;

• Early emerging fractions are more bold, they display more exploratory behaviour and recover faster from startling compared to intermediate and late emerging fish.

• There were no differences in SMR, MMR or the metabolic scope of different emergence fractions, however, early emerging fractions had a smaller oxygen debt following chasing, and repaid it quicker.

• Early emerging fractions had a smaller cortisol response following a low water level challenge, but mobilisation of glycogen stores did not differ between fractions.



Feeding



Starvation and refeeding

Early Middle Late p

BM INIT (g) 53.41 ± 1.67 51.93 ± 1.35 51.63 ± 2.19 0.751

BM FAST (g) 50.21 ± 1.56 49.31 ± 1.26 49.30 ± 2.11 0.908

BM RE-FED (g) 61.29 ± 1.86 64.02 ± 1.94 60.44 ± 2.93 0.524

SGR FAST (% d-1) -0.62 ± 0.04 a -0.52 ± 0.03 ab -0.46 ± 0.04 b 0.011

SGR RE-FEED (% d-1) 2.00 ± 0.15 2.60 ± 0.14 2.02 ± 0.25 0.050

BM abs loss (g) 3.20 ± 0.23 a 2.62 ± 0.15 ab 2.33 ± 0.20 b 0.013

BM relative loss (%) 5.98 ± 0.35 5.04 ± 0.24 4.53 ± 0.35 0.011

BM abs gain (g) 11.08 ± 0.95 14.71 ± 1.00 11.14 ± 1.52 0.065

BM relative gain (%) 22.19 ± 1.87 a 29.80 ± 1.74 b 22.71 ± 3.03 a 0.048

Gain:Loss abs 3.55 ± 0.33 a 5.74 ± 0.44 b 4.86 ± 0.56 ab 0.008



Conclusions (II)• Early emerging fractions had a higher rate of weight loss in the face of starvation, probably

linked to higher routine activity levels.• The intermediate group was most starvation tolerant, and gained weight faster during

refeeding.• Co-habitation of different emerging fractions did not reveal a competitive advantage of early

emerging fish under a restrictive feeding regime – again, the intermediate group outperformed the others.

Recommendations?Overall, the intermediate group appears to have the best characteristics for production in an ‘optimal’ environment.

Some fish farmers are currently using the early emerging fraction to put in sea cages. Production costs slightly more, but is more than met but reduced losses!

Emergence fractions do not always exist.8 February 2018Boldness in fishes / University of Stirling30


Thank you for your attention!Questions?

8 February 2018Boldness in fishes / University of Stirling

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